1. Field of the Invention
The present invention relates generally to network systems and, more particularly, to a system and method for re-balancing power supply efficiency in a networking environment.
2. Introduction
Energy costs continue to escalate in a trend that has accelerated in recent years. Such being the case, various industries have become increasingly sensitive to the impact of those rising costs. One area that has drawn increasing scrutiny is the IT infrastructure. Many companies are now looking at their IT systems' power usage to determine whether the energy costs can be reduced.
One of the challenges in addressing these energy costs relates to the efficiency of power usage. To illustrate this challenge, consider a large power over Ethernet (PoE) switch that contains 384 ports. Such a 384-port PoE switch can be configured in a variety of ways in responding to the ever-changing needs of an enterprise. For example, the 384-port PoE switch can change configurations by adding or removing a single 48-port PoE line card. Whether adding or removing a 48-port PoE line card, the change in power required to support or not support those 48 PoE ports can be significant.
In combination, the 48 ports can have a range of power consumption. For example, a single PoE Plus port can require a minimum of 60 W of four-pair power, while a standard PoE port can require 15.4 W of power. Thus, depending on the mix of PoE Plus ports, standard PoE ports, and non-PoE ports, the total power required by the 48-port PoE line card can range significantly. This range is only increased when considering the combined variance of eight line cards that can be included in the 384-port PoE switch. As would be appreciated, while the total power required to support the 384-port PoE switch can easily extend to 2 kW, the potential for usage of far less than 2 kW is also significant.
The power supply that supports network equipment has a power supply efficiency curve. An example of a power supply efficiency curve is illustrated in FIG. 1. Here, the power supply efficiency can be calculated by dividing the output power by the input power. As illustrated, the power supply efficiency is typically lower when the output power of the power supply is a small faction of the rated capacity of the power supply, and increases as the output power of the power supply approaches the rated capacity of the power supply.
In general, power supply manufacturers design a power supply to be efficient at a certain load point or narrow range of operation. Operation of a power supply at a non-optimal load point or range of operation will lead to operation of the power supply at a poor power efficiency.
For example, consider a power supply that can operate at 90% efficiency at a desired load point or range of operation. At 90% efficiency, the power supply would require, for example, 550 W of input power to produce 495 W of output power. In contrast, when operating at a non-optimal load point that has 70% efficiency, the power supply would require 707 W of input power to produce the same 495 W of output power. As this simple example illustrates, the efficiency of the power supply at a particular operational load point has a direct relation to the amount of input power needed to power the system.
For an enterprise, the operation of power supplies across the entire network infrastructure at a poor efficiency can lead to significant economic waste as more power than otherwise needed is required to power the network infrastructure. What is needed therefore is a mechanism for re-balancing power supply efficiency in a network environment.